寫在前面

最近在學vue.js，看到一個網站上有很多視頻教程，但在線觀看不能倍速播放，就想著用python爬蟲批量下載到本地。

安裝依賴

pip3 install requests

測試樣例

加上序言總共有16個視頻，我們用python爬蟲技術批量下載到本地。

https://learning.dcloud.io/#/?vid=0

獲取直鏈

首先我們要獲取視頻的下載直鏈。鼠標右擊檢查，可以直接看到視頻的直鏈。

再看一下頁面的源代碼，發現視頻的直鏈不見了，原來視頻直鏈的位置變成了一個js腳本。

如果我們直接用requets庫請求url的話得到的是源代碼，但是源代碼里面并沒有視頻直鏈，所以我們要考慮換個思路。為什么視頻直鏈的位置會被js替換呢？

爬蟲多了你就會知道，這是網頁的動態加載，一定有一個js文件里面保存了視頻的直鏈，然后每次加載網頁的時候，通過js腳本將視頻直鏈動態加載到html中。

點擊網絡，篩選js文件，找到了3個js文件，我們先看第一個js文件里面有沒有視頻直鏈。搜索視頻的標題，直接找到了視頻的直鏈，發現所有的視頻直鏈都被保存到一個名為lesson_list的變量。

lesson_list里面保存了所有的視頻名稱和視頻直鏈信息，這里為了統一，將序言改為第0節。

# lesson_list.py
lesson_list = [{
    "name": "第0節 vue.js介紹",
    "url": "https://vkceyugu.cdn.bspapp.com/VKCEYUGU-learning-vue/52d32740-aecd-11ea-b244-a9f5e5565f30.mp4",
    "ask": "77367"
}, {
    "name": "第1節 安裝與部署",
    "url": "https://vkceyugu.cdn.bspapp.com/VKCEYUGU-learning-vue/52dd6070-aecd-11ea-b43d-2358b31b6ce6.mp4",
    "ask": "77369"
}, {
    "name": "第2節 創建第一個vue應用",
    "url": "https://vkceyugu.cdn.bspapp.com/VKCEYUGU-learning-vue/52f3cea0-aecd-11ea-b997-9918a5dda011.mp4",
    "ask": "77370"
}, {
    "name": "第3節 數據與方法",
    "url": "https://vkceyugu.cdn.bspapp.com/VKCEYUGU-learning-vue/52eec590-aecd-11ea-b244-a9f5e5565f30.mp4",
    "ask": "77372"
}, {
    "name": "第4節 生命周期",
    "url": "https://vkceyugu.cdn.bspapp.com/VKCEYUGU-learning-vue/52e63a10-aecd-11ea-b43d-2358b31b6ce6.mp4",
    "ask": "77373"
}, {
    "name": "第5節 模板語法-插值",
    "url": "https://vkceyugu.cdn.bspapp.com/VKCEYUGU-learning-vue/52e72470-aecd-11ea-b997-9918a5dda011.mp4",
    "ask": "77375"
}, {
    "name": "第6節 模板語法-指令",
    "url": "https://vkceyugu.cdn.bspapp.com/VKCEYUGU-learning-vue/98c18710-aecd-11ea-b43d-2358b31b6ce6.mp4",
    "ask": "77376"
}, {
    "name": "第7節 class與style綁定",
    "url": "https://vkceyugu.cdn.bspapp.com/VKCEYUGU-learning-vue/4fe81fd0-aece-11ea-b997-9918a5dda011.mp4",
    "ask": "77377"
}, {
    "name": "第8節 條件渲染",
    "url": "https://vkceyugu.cdn.bspapp.com/VKCEYUGU-learning-vue/98bad050-aecd-11ea-b680-7980c8a877b8.mp4",
    "ask": "77378"
}, {
    "name": "第9節 列表渲染",
    "url": "https://vkceyugu.cdn.bspapp.com/VKCEYUGU-learning-vue/5da98c30-aece-11ea-b244-a9f5e5565f30.mp4",
    "ask": "77380"
}, {
    "name": "第10節 事件綁定",
    "url": "https://vkceyugu.cdn.bspapp.com/VKCEYUGU-learning-vue/98bd6860-aecd-11ea-8bd0-2998ac5bbf7e.mp4",
    "ask": "77381"
}, {
    "name": "第11節 表單輸入綁定",
    "url": "https://vkceyugu.cdn.bspapp.com/VKCEYUGU-learning-vue/656e12b0-aece-11ea-a30b-e311646dfaf2.mp4",
    "ask": "77382"
}, {
    "name": "第12節 組件基礎",
    "url": "https://vkceyugu.cdn.bspapp.com/VKCEYUGU-learning-vue/98a06a80-aecd-11ea-8bd0-2998ac5bbf7e.mp4",
    "ask": "77383"
}, {
    "name": "第13節 組件注冊",
    "url": "https://vkceyugu.cdn.bspapp.com/VKCEYUGU-learning-vue/98ed7910-aecd-11ea-b997-9918a5dda011.mp4",
    "ask": "78520"
}, {
    "name": "第14節 單文件組件",
    "url": "https://vkceyugu.cdn.bspapp.com/VKCEYUGU-learning-vue/79db90b0-aece-11ea-8a36-ebb87efcf8c0.mp4",
    "ask": "78521"
}, {
    "name": "第15節 免終端開發vue應用",
    "url": "https://vkceyugu.cdn.bspapp.com/VKCEYUGU-learning-vue/7e3b8f70-aece-11ea-8ff1-d5dcf8779628.mp4",
    "ask": "81004"
}]

批量下載

這里用for循環遍歷每一個下載鏈接，然后使用之前寫的一個多線程下載器下載。

from concurrent.futures import ThreadPoolExecutor
from lesson_list import lesson_list
from requests import get, head
import time


class downloader:
    def __init__(self, url, num, name):
        self.url = url
        self.num = num
        self.name = name
        self.getsize = 0
        r = head(self.url, allow_redirects=True)
        self.size = int(r.headers['Content-Length'])

    def down(self, start, end, chunk_size=10240):
        headers = {'range': f'bytes={start}-{end}'}
        r = get(self.url, headers=headers, stream=True)
        with open(self.name, "rb+") as f:
            f.seek(start)
            for chunk in r.iter_content(chunk_size):
                f.write(chunk)
                self.getsize += chunk_size

    def main(self):
        start_time = time.time()
        f = open(self.name, 'wb')
        f.truncate(self.size)
        f.close()
        tp = ThreadPoolExecutor(max_workers=self.num)
        futures = []
        start = 0
        for i in range(self.num):
            end = int((i+1)/self.num*self.size)
            future = tp.submit(self.down, start, end)
            futures.append(future)
            start = end+1
        while True:
            process = self.getsize/self.size*100
            last = self.getsize
            time.sleep(1)
            curr = self.getsize
            down = (curr-last)/1024
            if down > 1024:
                speed = f'{down/1024:6.2f}MB/s'
            else:
                speed = f'{down:6.2f}KB/s'
            print(f'process: {process:6.2f}% | speed: {speed}', end='')
            if process >= 100:
                print(f'process: {100.00:6}% | speed:  00.00KB/s', end=' | ')
                break
        end_time = time.time()
        total_time = end_time-start_time
        average_speed = self.size/total_time/1024/1024
        print(f'total-time: {total_time:.0f}s | average-speed: {average_speed:.2f}MB/s')


if __name__ == '__main__':
    for lesson in lesson_list:
        url = lesson['url']
        name = lesson['name']
        down = downloader(url, 8, name+'.mp4')
        down.main()

結果打印

16個視頻，總計339MB，用了56s就下載完了。

process:  100.0% | speed:  00.00KB/s | total-time: 2s | average-speed: 2.47MB/s
process:  100.0% | speed:  00.00KB/s | total-time: 3s | average-speed: 6.62MB/s
process:  100.0% | speed:  00.00KB/s | total-time: 3s | average-speed: 3.72MB/s
process:  100.0% | speed:  00.00KB/s | total-time: 4s | average-speed: 7.72MB/s
process:  100.0% | speed:  00.00KB/s | total-time: 4s | average-speed: 5.85MB/s
process:  100.0% | speed:  00.00KB/s | total-time: 7s | average-speed: 7.01MB/s
process:  100.0% | speed:  00.00KB/s | total-time: 3s | average-speed: 4.65MB/s
process:  100.0% | speed:  00.00KB/s | total-time: 4s | average-speed: 6.69MB/s
process:  100.0% | speed:  00.00KB/s | total-time: 3s | average-speed: 5.88MB/s
process:  100.0% | speed:  00.00KB/s | total-time: 4s | average-speed: 5.01MB/s
process:  100.0% | speed:  00.00KB/s | total-time: 3s | average-speed: 6.60MB/s
process:  100.0% | speed:  00.00KB/s | total-time: 4s | average-speed: 6.20MB/s
process:  100.0% | speed:  00.00KB/s | total-time: 3s | average-speed: 5.96MB/s
process:  100.0% | speed:  00.00KB/s | total-time: 2s | average-speed: 4.64MB/s
process:  100.0% | speed:  00.00KB/s | total-time: 3s | average-speed: 6.02MB/s
process:  100.0% | speed:  00.00KB/s | total-time: 4s | average-speed: 6.80MB/s

總結展望

有時候視頻或圖片的直鏈不一定需要爬取，在網頁加載的js文件里面說不定就能找到。既然能直接找到，我們何必爬呢？然后下載的時候一定要采用多線程，因為多線程可以占滿寬帶實現滿速下載。

引用參考

https://blog.csdn.net/qq_42951560/article/details/108785802

總結

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